Speaker after speaker called for a rethink during a debate at the party’s spring conference in Sheffield.

Former Cabinet minister Baroness Shirley Williams branded the changes “lousy”, while backbencher Andrew George insisted the party should not be “the architects of (the NHS’s) demise”.

Amendments to a motion put forward by Health Minister Paul Burstow were passed almost unanimously by activists.

They objected to the “damaging and unjustified market-based approach” being taken by the Government.

“Conference regrets that some of the proposed reforms have never been Liberal Democrat policy, did not feature in our manifesto or in the agreed Coalition Programme, which instead called for an end to large-scale top-down reorganisations,” the text stated.

Lady Williams said she did not want to damage Mr Clegg or the coalition.

But she insisted the Deputy Prime Minister was allowing the “treasured” health service to be put at risk.

“We did not expect a massive reorganisation and one which will fall within a period when many of our fellow citizens are worried about whether they will keep their jobs and how they will pay for petrol and food,” she said.

Lady Williams warned that the “accountability proposals of the new structures are lousy”, and private companies would be looking to “cherry pick” profitable services rather than treat patients in the most need.

She said the party rank-and-file had to “stand up and be counted” by opposing the plans.

“In doing so we will make the coalition a better coalition,” she added.

St Ives MP Mr George told the gathering it was natural for incoming governments to trash the record of their predecessors.

“But don’t trash the NHS,” he added. “This is a dream come true for litigators, lawyers and management consultants.

“The Lib Dems were the architects of the NHS. Don’t let us become the architects of its demise.”

Fellow backbencher John Pugh dismissed plans for more democratic involvement in local health services as a “sop” designed to win over the Lib Dems.

He said the reforms would actually create the “biggest quango in the country”, suggesting that only Tory health secretary Andrew Lansley thought they were a good idea.

“It is no longer the doctors who know best, it is the minister,” Mr Pugh said. “We have the Government on the one side and the NHS on the other.”

Former MP Sandra Gidley asked the conference: “How can it be right to put such power in the hands of GPs who for the most part do not want to do it and are not qualified?”

Responding to the conference’s vote, Mr Burstow said he would be “taking those concerns back to Government”.

“The Liberal Democrats are fundamentally committed to the NHS. We believe in an NHS that is universal, based on need and free at the point of use,” he said.

“There will be no US-style privatisation of the health service on our watch.

“The party has shown its mettle by setting out areas for improvement in the Bill.

“I can assure you we are listening to the party’s concerns and I will be taking those concerns back to the Government.”

Former MP Dr Evan Harris, one of the driving forces behind the main amendment, said he wanted Mr Clegg and the leadership to “seize the opportunity” to secure fundamental changes to the Bill.

And Dr Charles West, who proposed the text, warned that there was a “serious potential for conflicts of interest”.

“Will your GP be looking after you or the budget?” he asked.

He said the coalition’s plans would increase the “creeping privatisation” in the NHS, encouraging “cut-throat competition”.

Shadow health secretary John Healey, who sat in on the debate in Sheffield, said: “This debate has forced a big climb down for Nick Clegg and his ministers, and the conference delegates have made it clear that David Cameron’s reckless NHS plans are not Lib Dem policy.

“They have shown today that they don’t want their party to get dragged down by the damage the Tories are trying to do to the health service.

“The big test now is for Nick Clegg, and it will be for him to persuade David Cameron to make fundamental changes to the planned legislation and reorganisation.

“Ordinary Lib Dem members should make common cause with everyone else who wants to protect the NHS and make sure he does.”

After the debate, Dr Harris said: “Because the health reforms were not in the coalition agreement, today’s vote is the only view expressed by the party on the subject, and sends a very clear message through the minister and our leader to their Conservative Coalition partners that we will not accept market reform of the health service, any fragmentation or destabilisation of NHS services by new private providers or the lack of accountability for the spending of public money envisaged in the model of GP commissioning promoted in the bill.

The onus is now on the Government to respond fully to the democratically expressed views of the Liberal Democrats.”

During a question and answer session later, Mr Clegg insisted “almost all” the amended motion went “with the grain” of the Government’s reforms.

“I am now going to look at it in considerable detail,” he said. “Because I think a lot of what we have talked about this weekend - greater accountability, greater transparency, making sure we don’t have a wilful disruptive approach to diversity of providers and don’t allow the profit motive and price competition to run a coach and horses through the NHS - that’s precisely what happens.”

He also launched an impassioned defence of the compromises he had made to enter coalition with the Tories.

“I am not going to make any apology for playing my part in making this a successful government,” he said. “You either accept as a party of pluralism that has wanted for generations to put an end to the old pendulum politics of blue red blue red...you cannot do that without taking risks.”

A clearly fired-up Mr Clegg said that at a conference event last night he had been approached by one activist who urged him to look happier when he was with David Cameron, and another who had told him not to smile so much.

“Make your minds up!” he insisted.

Before taking the next question, the Deputy Prime Minister added: “Now, who else wants some more of that?”

Responding to a student who asked how he should explain the tuition fee hike to his friends, Mr Clegg said bluntly: “We were really stuffed on this one. We were isolated because both other parties, Labour and the Conservatives, agreed more with each other than they did with us.

“Even if we had gone into coalition with Labour fees would have gone up.

“It’s a sort of reality check to realise that when you come third in an election and you’re trying to decide whether to go into a coalition you have no leverage at all when two other parties basically agree with each other.”

He also dismissed the idea of universities charging high fees to maintain their prestige.

“I can’t think of anything more absurd than a university saying to provide a good education they have to whack up the price to £9,000,” Mr Clegg added.